Refrigeration system and expansion valve therefor



Feb. 4, 1947. CARTER I 2,415,338

REFRIGERATION SYSTEM AND EXPANSION VALVE THEREFOR FilOd April 20, 1945 mmvmn. guakfirw .M/ BY I W K, M

Azu ATTORNEY Patented Feb. Q, 1947 REFRIGERATION SYSTEM AND EXPANSION VALVE THEREFOR Franklyn Y. Carter, Deal-born, Mich., assignor to Detroit Lubricator Com pany, Detroit, Mich., a corporation of Michigan Application April 20, 1945, Serial No. 589,330

Claims.

- 1 [This invention relates to refrigerating sysitems and particularly to a system having a thermostaticexpansion valve and having a compressor driven by an electricmotor.

In'refrigerating systems having an air cooled ternally screw threaded open end I! alined with the valve port. The valve member I5 is controlled condenser, the high side pressure or compressor ;head pressure will increase with increase in ambient temperature. The motor which drives the compressor must be of sufllcient size or power to carry the load at all ambient temperatures. During the summer there are peaks of high ambient temperature which require in effect an- 'ioversize motor, but the size of the motor could be materially reduced if the peak loads were eliminated.

It is therefore one object of this invention to provide means to limit the load on the motor so that it will not be overloaded at the peak temperatures.

Another object is to provide means to increase automatically the superheat setting of the. expansion valve so as to limit the load on the motor.

The invention consists in the improved conw'struction of and combination of parts, to be more fully described hereinafter and the novelty of which will be particularly-pointed out and distinctly claimed.

In the accompanying drawing, to be taken as ,8. part of this specification, there is fully and clearly illustrated a preferred embodiment of the invention, in'which drawing the figure is a diagrammatic view of a refrigerating system showmg in section a'thermostatic expansion valve and means for automatically increasing the superheat setting of the valve.

Referring to the drawing by characters of reference, ldesignates generally a refrigerant compressor driven by an electric motor 2- and discharging compressed refrigerant through a conduit 3 to an air cooled condenser 4. From the condenser ithe refrigerant liquid line or conduit '5 connects to the inlet 6 of the thermostatic expansion valve 7 havingits outlet 8 connected by a conduit 9 to the inlet of an evaporator or cooling coil l0. The outlet of the evaporator is connected by a refrigerant suction line or conduit H ber-t5, positioned in a valve chamber l6 which c'onnectswith the outlet 3 and which has an inin the usual manner by a liquid charged temperature responsive power element 18 having a feeler bulb I9 clamped to the suction line H adjacent the outlet of the evaporator III. The power element l8 has a movable wall or diaphragm 20 acting through one or more push pins 2| which engage the valve member I5 so as to move the valve member to open position in accordance with the temperature affecting the bulb l9. One or more of the guideways 22 for the' pins 2| is of sufficient cross section to provide clearance space for transmission of the system low side pressure or evaporator back pressure to the pressure chamber 23 having one of its walls formed by the diaphragm 20 so that the low side pressure tends to close the valve member IS;

The superheat setting of the'valve 1 is determined by the force of spring 24 positioned in the chamber i6 and acting to close the valve member 15 and also acting through the pins 2| to oppose opening of the valve by the power element Ill. The spring 24 is supported by a longitudinal thrust rod or member 25 carried by a casing 26 having an end wall or cap member 21 with an extended portion 28 which is externally screw threaded as at 29 for adjustable engagement with the threads ll of the valve chamber l6. Within the casing 26 there is a pressure responsive member or bellows 30 which is sealed to the casing as at 3| and which divides the casing internally into a low pressure chamber 32 and a surroundi ing high pressure chamber 33. The low pressure chamber 32 connects with the outlet 8 and the valve chamber I6 through a port or passageway 34 extending lonigtudinally through the extended portion 28. The joint between the ex-v tended portion 28 and the expansion valve casing is sealed by solder or the like as at 35 after adjustment of the spring 24. The cap member 21 is also sealed to the side vwall of the casing 26 as at 36. Within the casing 26 there is a spring 31 which surrounds the'thrust member 2 5 and which is held under compression between the end wall 2'8 and the pressure responsive member 30. The thrust member 25 rests on the responsive 'member 30 so that upward movement of the mem ber 30 by pressure in the chamber 33 will increase the'force of the spring 24 in opposition to the power element It and thereby increase the superheat setting of the expansion valve; The

high pressure chamber 33'has an inlet 38 to re ceive a conduit 39 which connects the chamber 3 33 to the refrigerant high side pressure and particularly to the liquid line 5.

The operation of the system is as follows: As long as the load on the motor 2 is normal so that the motor is not overloaded, the system will operate in. the usual manner with the evaporator l completely flooded and. the valve 1' operating at the usual superheat setting of say, 4 F. If,

however, the temperature surrounding the consuperheat setting of the valve 1 is automatically 7 increased upon any further increase of head pressure so that the load on the motor 2 will not have any further increase. If, for example, the pressures which will full load the motor 2 at the superheat setting of 4 F. are a pressure of say. 220 pounds per square inch, compressor head pressure or high side pressure and a pressure on the low side of the system or a refrigerant back pressure of say, 50 pounds per square inch, then the spring 31 acting with the spring 24 will hold the responsive member 30 against movement up to this diilerential pressure of 170 pounds per square inch. However, if the temperature surrounding the condenser 4 now increases, it would increase the high side or head pressure and the motor 2 will be overloaded. The increase in headpressure will be transmitted to the chamber 33 through the conduit 39 and will overcome the combined forces of springs 31 and 24 so that the responsive member will move the thrust member 25 upward. This will compress and increase the force of spring 24 acting in opposition to the power element 18 and thereby increase the superheat setting of the valve which will result in a reduction of the refrigerant back pressure and thus decrease the load on the motor 2. The increase in the superheat setting of the valve 1 will, of course, bein accordance with the difference of the pressures in the chambers 32 and 33 as determined by the spring 31 acting with the spring 24. Although the evaporator ill will be starved in accordance with the increase in superheat setting above its normal setting of say, 4 F., the motor 2 will not be overloaded for any increase in the ambient temperature around the condenser 4 and which causes an increasein compressor head pressure.

What is claimed and is desired to be secured by Letters Patent of the United States is: v

1. In a refrigerating system, means for limiting the load on the refrigerant compressor motor comprising a thermostatic expansion valve having a casing with an inlet and an outlet and a valve chamber, a valve member in said valve 'the differential refrigerant pressure to move said thrust member.

2.A refrigerating system, comprising a. compressor, a condenser and an evaporator communicatively connected together, an electric motor for driving said compressor, a thermostatic expansion valve having means responsive to low side refrigerant back pressure and temperature and having a valve member controlled by said means and controlling flow of refrigerant to said evaporator, a spring compressed against and urging said valve member toward closed position and determining the superheat setting of said valve, operating means movable by a predetermined difference of refrigerant pressures on the high and the low sides of the system, and means actuated by said operating means and cooperable with said spring to increase the compression of said spring against said valve member thereby to increase the superheat setting of said valve.

3. A refrigerating system, comprising a compressor, a condenser and an evaporator communicatively connected together, an electric motor for driving said compressor, a thermostatic expansion valve having a valve member controlling flow of refrigerant to said evaporator, a spring urging said valve member toward closed position and determining the superheat setting of said valve, a casing carried by said expansion valve and alined with said spring, a thrust'rod supporting said spring andextending into said casing, a pressure 1 4. In a refrigerating system, means for limiting the load on the refrigerant compressor motor comprising a thermostatic expansion valve having a casing with an inlet and an outlet and a valve chamber, a valve member in said valve chamber, a'spring in said valve chamber urging said valve member toward closed position and determining the superheat setting of said valve, a casing closing said valve chamber and alined with said spring, a thrust rod supporting said spring and extending into said second-named casing, a pressure responsive member in and dividing said second-named easing into a low pressure chamber and a high pressure chamber, means connecting said low pressure chamber to the low pressure side of the system, means connecting said high pressure chamber to the high pressure side of said system, said responsive member engaging said thrust rod and being operable to move said rod to compress said spring to increase the superheat setting of said valve, and a spring in said second-named casing opposing movement of said thrust rod by pressure in said high pressure chamber and determining with said superheat determining spring the pressure diiference between the pressure in said high pressure chamber and in said low pressure chamber at which said responsive member will move said thrust rod.

5. The combination with a thermostatic refrigerant expansion valve having a valve chamber containing a valve closing and superheat determining spring of means for increasing the force exerted by said spring upon the occurrence of a predetermined difference of pressures between the inlet and outlet of the valve, comprising a casing having an end wall with an extending por- 5 tion alined with said spring and closing said valve chamber, said end wall and extending portion having a guideway therethrough alined with said spring, a thrust rod reciprocal in said guideway and supporting said spring, a pressure responsive member in said casing and dividing said easing into a high pressure chamber and a low pressure chamber and operable to move said rod to comsaid high pressure chamber and determining with said superheat spring the difierence in the pressures in said high and low pressure chambers at -which said rod will be moved to compress said superheat spring.

FRANKLYN Y. CARTER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,258,458 Lange Oct. 7, 1941 

